We've carried charcoal going back quite a ways now, and like some have said, it's not used that often. For us, statewide, it requires a medical consultation.
Removing something because "It's not used often and people forget" is a pretty asinine reason. Hell, on that line of thought lets remove NG/OG insertions and intubation for any medics doing less than 15 a year. I'm certain that people will spend the extra time keeping those skills fresh w/ con ed and practice, as opposed to remembering/relearning situations when (and when not) to administer a cup of mud.
Citing several studies done in late 70's & 80's, many of them suggest the timeframe to achieve the
BEST results for parenteral toxicological emergencies using activated charcoal, is to give the drug (with or without lavage is debatable) within 30min to 2hrs of ingestion of the toxins. One study even suggested a positive effect within 4 hrs of ingestion.
Sure, many of our PO toxicological emergencies don't present themselves within that timeframe. However for those that do, or are on the cusp, does it not serve the pt to administer a treatment following a thorough assessment and a consultation w/ poison and/or med control?
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2014891/
http://www.ncbi.nlm.nih.gov/pubmed/10417490
http://www.ncbi.nlm.nih.gov/pubmed/7109006
(this last link disputes the efficacy of charcoal following prolonged ingestion periods)